The investigators previous research has demonstrated that proteoglycan 4 (PRG4) may be a biomarker for identification of severity in COPD. PRG4 was more sensitive and specific than CRP for confirming COPD severity and acute exacerbation frequency. It was related to the 1-year force vital capacity decline in COPD patients. The past study found that Prg4 is an immunomodulatory factor regulating parathyroid hormone actions on hematopoietic cells in mice. Previous report showed that voluntary wheel running and fluid flow shear stress that promote the expression of the Prg4 and association with pulmonary inflammation. COPD patients are characterized by a progressive decrease of lung function that is associated with increased in the airway and systemic inflammation. Pulmonary recovery (PR) is able to decrease acute exacerbation, maintain pulmonary function, increase exercise tolerance and improve quality of life in COPD patients, but it is unknown the mechanism of PRG4. The current study aimed to study in the pulmonary inflammation and the effectiveness of pulmonary recovery in COPD Patients：The mechanism of PRG 4.